Delete the uesless defs.h file
Use the Makefile.common for all unit tests

Previously there is an individual Makefile for all unit tests. We
replace them with the newly created Makefile.common.
Ignore the trace data file and tracer exe
Ouput to /dev/null when load the -dgiri pass

The output of the .bc file was supposed to be the same one as the
original one generated by 'clang -emit-llvm'.
Remove counter and invFail memeber from TraceFile

These two variables were used by the diagnose project. We deleted them
safely here and run the unit test to verify.
Using namespace giri/dg instead of repeated giri::

This kind of style makes the code more compact. This is a trivial commit
and not big deal.